help about: anova and population no normal
Oh, and to answer your question more directly, the randomization test permits testing hypotheses using any metric, so scale & shape are definitely testable. Typically one is interested in means, so on each iteration of the test loop one computes the group/condition means. However, it's simple to instead compute, say, the best fit weibull to each condition and simultaneously test shift, shape, and scale.
On Tue, Mar 31, 2009 at 12:18 PM, Mike Lawrence <Mike.Lawrence at dal.ca> wrote:
Those with more formal statistical backgrounds may provide better advice, but in my own informal training I've come to wonder why parametric stats persist in the face of modern computing power. As I understand it, Fisher developed ANOVA as low-computation method of approximating the Randomization Test (a.k.a. exhaustive permutation test). Where computation power has grown exponentially since Fisher's time, these days it is feasible to compute the full R-Test in many cases, and for those cases where the full R-Test ?is not feasible, non-exhaustive permutation variants usually satisfy. Indeed, it has been shown (http://brm.psychonomic-journals.org/content/37/3/426.short) that the R-Test is more powerful than the F-Test in the face of skewed distributions. My advice would thus be to abandon parametrics and simply code a randomization test variant of the ANOVA you want. Mike On Tue, Mar 31, 2009 at 10:29 AM, Sarti Maurizio <sarti.m at irea.cnr.it> wrote:
Dear R-Helpers, Parametric statistics are statistics where the population is assumed to fit any parametrized distributions (most typically the normal distribution). My problem is: 1) if my polulation is no normal 2) if the sample data of all replications and treatments were well fitted from the Weibull distribution (shape and scale parameters). Can be The shape and scale parameters compared between treatments by using the canonical analysis of the variance ANOVA? Many thanks for your help with these questions. Maurizio
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-- Mike Lawrence Graduate Student Department of Psychology Dalhousie University Looking to arrange a meeting? Check my public calendar: http://tinyurl.com/mikes-public-calendar ~ Certainty is folly... I think. ~
Mike Lawrence Graduate Student Department of Psychology Dalhousie University Looking to arrange a meeting? Check my public calendar: http://tinyurl.com/mikes-public-calendar ~ Certainty is folly... I think. ~